Our invention relates to femoral prostheses and in particular to prostheses adapted for non-cemented fixation in the medullary canal of a femur.
Various types of femoral prostheses are known and are used for surgical reconstruction of a femur. In general, these prostheses comprise a ball-shaped head mounted at an anatomical angle on a shank. The shank can be thrust into a medullary canal of a femur to mount the prosthesis on a resected surface of the femur. Various means of fixation are known, including bone cement, or porous areas on the prosthesis which promote bony ingrowth, or shoulders proximal to the head for preventing the prosthesis from wedging into the medullary canal.
In femoral prostheses which are particularly adapted for non-cemented applications, initial fixation and subsequent bony ingrowth are important features. Micromotion of the prosthesis may result in reduced fixation, compromising the long-term stability of the prosthesis. At the same time, variation in human anatomy makes it difficult to provide a wide range of tightly fitting sizes for femoral prostheses. Thus, there remains a continuing need for improvement in the design of non-cemented prostheses which provide for firm initial fixation while simultaneously avoiding the possibility of overloading the surrounding bone.